What voltage are the signals from the RC receiver you are using? I ask because a lot of the PIC32 I/O lines don't seem to be 5 volt tolerant, especially on on the smaller packages like the PIC32MX250F128B etc. I know having built a few multi-copters myself, that RC receivers can have a lot of channels. I have mostly used ATmega chips which run on 5volts, I haven't tried a PIC32 as a flight controller yet, though no doubt will one day.